Broken means a kit design problem, which he sure fucking has, overpowered is a number problem.
Right now Zed is over powered by all definitions except for people who just try to stretch the definition of overpowered to fit their needs.
Currently classified as S+ tier for mid on U.GG and here are his per rank stats (from U.GG, I'll give them in this order, win, pick, ban)
- Iron: 50.54%, 15.1%, 42.5%
- Bronze: 49.9%, 16.3%, 47.6%
- Silver: 50.23%, 14.5%, 51.8%
- Gold: 50.88%, 13.2%, 51.6%
- Platinum: 51.52%, 12.5%, 46.6%
- Diamond: 51.76%, 11.8%, 35.5%
- Master: 52.66%, 10.3%, 22.5%
- Grandmaster: 53.2%, 11.5%, 21.4%
- Challenger: 58.26%, 11.3%, 13.7%
I mean, at that play rate and ban rate, 49.9% can't even be considered a negative win rate, so basically, Zed has huge play rates, no negative winrates across the board and is considered one of the hardest champs to play in the game, one of the easiest to counter and he's not good in places where people communicate a lot and know how to play, yet his highest win rate is in Challenger, where people know how to counter, where people know how to play and they communicate. If he was so easy to counter and all you had to do is build Seeker's to "nullify all his damage" as everyone sais, why is his lowest win rate in places where people DON'T BUILD SEEKER'S yet his highest is where people know how to counter him?
He may need a lot of skill and mechanical knowledge to play to perfection, that's true and I won't deny it, but his skill floor.....I'd probably put him at Tryndamere level. If he didn't had such play rates in low elo, his win rate in his current state would be much higher.
Let's compare to Riven for example, who's a champion called "OMFGBBQOPBROKENMETA" by pretty much everyone here, or at least, the vast majority:
- Iron: 44.33%, 5.3%, 2%
- Bronze: 45.5%, 5.5%, 2.1%
- Silver: 47.8%, 6.7%, 2.8%
- Gold: 49.8%, 8.4%, 4.2%
- Platinum: 51.07%, 10.1%, 6.8%
- Diamond: 52.76%, 11.8%, 12.6%
- Master: 54.03%, 10.7%, 16,6%
- Grandmaster: 54.35%, 11%, 20.7%
- Challenger: 53.62%, 11%, 19.8%
So she only wins more than Zed between Diamond and Grandmaster and is only banned more than him in Challenger, yet she's always played less than him. If Zed had her play rate in Iron, Bronze and Silver, he'd be close to 60% there, but even at almost triple her play rate, he's still in positive win rates, yet she's.....well, struggling so to put it. Yes, Conqueror, DD and Spear make her strong, but she's still hard to play. Is she stronger than she needs to be? A bit, yes, but she still shows she's hard to play, look at the stats. If she's over powered, then Zed outclasses her by a lot.
(all stats are in each's main lane, no Support Riven or JG Zed interfering with their stats)
Zed needs nerfs, starting with his passive being stopped from working on creeps. Wanna know why he has such a high win rate in lower elos? He farms too easy, with his 30 free bonus damage for LH from his passive, making him get his items too easy, and Zed has no issues killing with items, even if he misses Q, since that's the skill he maxes first, and that shouldn't happen unless the enemy is like 200 HP, but in that case, why the hell didn't you back off when against an Assassin?